[Erron Spalsbury]

Originally Posted by bluemax_1

lethal,

you're right that Stoptech doesn't necessarily do track testing with each platform, but I've read up on the tests they do on the individual platforms while they're developing/customizing their brakes for the platform and the testing, although simple, achieves the purpose which is to optimize the brake balance bias for front and rear. The track testing data that they gather is to provide more information on things like heat management, rotor wear, caliper fatigue, etc. to see if there are any potential problems from consistent track abuse of their brakes.

prerunner,

keep in mind that in most cases, there is only ONE real reason for getting a BBK (other than aesthetics), and that is thermal management. Although a larger rotor can potentially lead to greater braking torque at that axle, due to the caliper being mounted further from the rotational axis (therefore increasing torque, if all else is the same), if this changes the brake bias to sub-optimal, then you're losing out. The Stoptech's might decrease braking distances (getting stickier tires and/or stickier pads will see a more significant change) but The MAIN reason for larger rotors is because rotors are heatsinks.

Brakes function by converting kinetic energy to heat by way of friction. Any given rotor has a thermal limit. Once you reach this limit, the rotors cannot easily absorb additional heat, and every consecutive braking event increases the rotor (and pad's) temperature significantly. Since all pads have a MOT (maximum operating temperature), once the temp exceeds this, you experience pad fade, and you can't stop. The more heat your rotors can absorb/dissipate, the more resistant they are to heat induced fade at the track or under hard use.

However when it comes to braking torque, if you can lock up your wheels with your brakes, they generate more than enough brake torque for the tires you're using. If you want to increase ONLY braking torque (say, after you get grippier tires), then the easiest thing to do is get brake pads with a higher Mu (friction coefficient). The reason to get a bigger brake kit with bigger rotors is because the larger rotors can accept more heat to withstand repeated hard braking.

Also, given 2 equal setups, the rotor with more mass has a better thermal capacity. But not all rotors are created equal. Thermal capacity is one thing, heat dissipation is another thing. If you believe Stoptech, their rotors have better heat dissipation than any others due to the design of their rotors, hats and calipers. What impressed me was some pics of the rotors they used on a BMW in an endurance race. Where other teams changed their rotors at least once in the race, the team with Stoptechs used the same rotors throughout and they were still good.

Like I said, the only real reason to get something like the ST 355mm kit is if you plan to push your car hard at the track. For occasional track use, folks have found that some simple upgrades have provided good bang for the buck. Things like:
Porterfield cryo rotors
Neo Super Dot, Motul RBF 600 or ATE fluid
Dedicated track (higher MOT) pads
Do-it-yourself brake ducts to improve brake rotor/system cooling.
Stainless lines

Those simple upgrades have been fairly effective on shorter, slower tracks, but if you start generating much more HP or get on longer tracks where you can develop more speed (or you simply want to push as hard as you can without worrying about babying your brakes), then it's time for a BBK.


Max

PS. forgot to mention something about wheels. Yep, they're big kits. The Stoptech 355mm will fit in stock 18" TT wheels though because the ST calipers actually take up less depth than the stock Sumitomo calipers On the same wheels, My Stoptechs have about 3-4 mm MORE depth clearance (clearance from the spokes) than the stockers. But the 355mm kit needs at least 18" wheels to fit. I don't think ANY 17" will fit, but any 18" wheels that clear the stock 2G TT calipers AND don't have odd spokes that curve in when they're near the rim, or have odd diametric reductions in the rim (Enkei RPF1 18x9.5 et+38mm have both those making them unusable) they should fit the Stoptech kit. No idea about the Brembos and clearance.

First off, that's the best posted reply i've seen on 3si in a few years. Very refreshing!

I've had the AP kit for a number of years now. Only a few issues overall. Not a biggie, but due to rotor temp the once anodized black hat, is now gold. Here's the biggie..
The first race I had with these they performed very well. ATF fluid freshly bled, 3" brake coolers, and the Pagid pads, worked like a charm. However, when returning to the shop to refresh the car for the next day, I found that a number of the bolts that hold the hat to the rotor had broke. Yes, broke. Bolt part still in there, but the nut side was now gone. I had 3-4 bolts left on each rotor that were still intact, scary stuff. A quick phone call to AP, told them story, and they waived the $180 for shouldered race bolts. They came with bolts that were threaded all the way down, apparently an option that I was not informed of during the purchasing process. Oh well, all has been good since with the upgraded harware. Short story, sorry for straying off topic..

The Stoptech's are awesome. I know a number of racers that use them and love them. I would listen to Max and find a good sized rotor for the fronts. Bigger is better when it comes to heating. Like Max said, it's a heat sink. The longer it takes to heat them, the better the cooling ducting will work, and ultimately a better performing braking system. Rotors will be replaced at some point, so look at replacement costs too. You can always to go to a different rotor as well. Even larger if you want to fab up new brackets. The calipers you'll hopefully have for a long time, so look into rebuild kits. Make sure they offer rebuild kits. Also look into whether or not they have dust boots. Those are critical for keeping the seals alive over extended periods of time. If you plan on endurance racing look into the removal of the pads, can it be done quickly? That's one of the main reasons I went to the AP's, they can be swaped in seconds, not minutes. (as long as your pit guy doesn't burn himself and run away like a little sissy, but that's another story) Even though i've never owned a set of stop techs, I would certainly recommend them, they have an awesome rep in the industry and they perform well from what i've seen. Take a look at Willwood too just for comparison....

Erron S.